1. Field of the Invention
This invention is directed to a system and method for identifying an unknown compound using pattern recognition of spectra. More particularly, this invention is directed to a system and method for identifying an unknown compound using a spectrum pattern obtained from a spectrum such as an infrared absorption spectrum, and comparing the individual peak relationships in the spectrum pattern to the peak relationships in spectra patterns of known compounds to identify the unknown compound.
2. Background Information
Today the modern spectroscopist can enlist the valuable aid of a computer integrated with the analytical instrument of choice. This computer is used not only to help with the generation of the spectrum, but also with the identification of the spectrum produced. There is presently a growing interest to find new integrated methodologies to both collect and analyze spectral data. One such analytical technique is referred to as pattern recognition, which has been described further in the literature in, for example, J. Schurmann, Pattern Classification: A Unified View, of Statistical and Neural Approaches (John Wiley & Sons: New York, 1996); B. Ripley, Pattern Recognition and Neural Networks (Cambridge University Press: Cambridge, 1996); C. M. Bishop, Neural Networks for Pattern Recognition (Clarendon Press: Oxford, 1995); J. Wood, Pattern Recognition, Vol. 29 no. 1, pp. 1-17 (1996); Y. Smetanin, Pattern Recognition and Image Analysis, Vol. 5 no. 2, pp. 254-293 (1995); and the application of pattern recognition to the infrared analysis of water samples is described in T. Witelski et al., Intent. J Environ. Anal. Chem., Vol. 44, pp. 127-136 (1990).
Computer based pattern and image recognition systems employing digital signal processing techniques have found many applications throughout science and industry. Typically, digital filters are custom designed for the particular application at hand, and are often computationally intensive. Disclosed herein is a system and method for identifying an unknown compound which employs a pattern matching technique that is flexible and computationally feasible, yet effective. Additionally, the present invention provides a useful form of visual feedback regarding the match between two patterns (referred to herein as waveforms, arrays, or spectra) that can be used to ascertain the nature of the difference between two waveforms.
In one preferred embodiment, the invention described herein employs infrared (IR) spectra. An important aid to chemists for the identification of organic compounds is the use of the infrared portion of the electromagnetic spectrum between 4000 cm−1 and 400 cm−1 (2.5-25 microns). It is well known that even the simplest of organic compounds is capable of generating a complex IR spectrum. These spectra are displayed as plots of percent transmittance vs. wavenumber, or as absorbence vs. wavenumber. For successful identification of a targeted compound, the sample in question should be relatively pure, and its spectrum adequately resolved and of reasonable intensity. The analyst must also use care to insure that the spectrophotometer is calibrated. Each compound's spectrum is generally unique, allowing the analyst to compare the unknown reagent to a reference compound.
The present invention employs a computer aided pattern recognition technique for analyzing the infrared spectra of organic compounds. Additionally, the technique is easily adapted to the analysis of different kinds of spectra produced by other instruments, such as a Raman spectrometer.
It is one object of this invention to provide a method of identifying unknown compounds using pattern recognition of spectra. It is another object of this invention to provide a system using a computer and pattern recognition of spectra to identify unknown compounds. Other objects, features and advantages of this invention will be apparent to those skilled in the art from the following detailed description of the invention.